Bricked an E5 dev kit by going straight to low power mode?


I was trying to measure the minimal current draw of the E5 dev kit, so created a new project with no peripherals configured and which goes to sleep right before the standard while loop. So there is no means of waking it up once it’s running.

Since flashing that code to the board, I cannot connect to it with STM32CubeProgrammer or a Segger J-LINK. STM gives the message “Error: No STM32 target found!”. I’m using the ST-LINK on a Nucleo board which was working fine for a couple of days worth of experiments and can still talk to another E5 dev kit.

I notice the warning ok the wiki which says:

  • The “PB13/SPI_SCK/BOOT” pin on the LoRa-E5 module is just a normal GPIO, not the “BOOT0” pin of the MCU. This “PB13/SPI_SCK/BOOT” pin is used in the bootloader of the Factory AT firmware, to decide to jump to APP or stay in bootloader(for DFU). The real “BOOT0” pin doesn’t pinout to the module, so users need to be careful when developing the low-power applications.

This is pretty unhelpful - what care should I have taken?

I was still able to communicate with the board when it was running the low power example, that wakes up every couple of seconds via an interrupt.

Looking at the current draw, when the reset button is held down it is 1.5mA and when the button is released it goes to 0.544uA.

Have I bricked the device?